This invention relates to a valve and, more particularly, to a valve for sampling a fluid flowing in stream for analysis and returning the sampled fluid to the stream.
Dzula, Levine and Sperry in their U.S. Pat. No. 4,018,089 disclose an apparatus for diverting a portion of a process fluid stream to contact a sensor device. Valves are provided away from the main process fluid stream to isolate the sensor from the fluid stream for removal of the sensor without shutdown of the fluid stream. However, fluid flow in the main process stream must be stopped in order to clean the ports which extend into the main process conduit while causing a stagnant area between the main fluid stream and the shutoff valves when the valves are closes.
Murdock, U.S. Pat. No. 4,727,758, discloses a flow-through sampling device for filtering a portion of a fluid side stream which provides a means for removal and cleaning of the sample chamber without shutdown of the main fluid flow. However, the pump cannot be removed for servicing without shutdown of the process stream.
Jiskott, U.S. Pat. No. 4,307,620, discloses a device for obtaining a homogeneous sample from a fluid stream by removing liquid from a main pipeline and returning it through a return loop upstream of the inlet to the return loop through mixing jets to agitate the fluid to obtain a substantially uniform mixture. In the event that plugging of the return loop lines occurs, it is necessary to stop fluid flow in the main pipeline.